Store Ruboty's memory in Redis.
# Gemfile
gem "ruboty-redis"
REDIS_SAVE_INTERVAL - Interval sec to push data to Redis (default: 5)
REDIS_URL - Redis URL (e.g. redis://foo:bar@example.com:6379/)
REDISTOGO_URL - Another Redis URL (At least one Redis URL is required)
REDIS_NAMESPACE - Redis name space (default: ruboty)